Organic nutrition for ewes in late pregnancy

There is a huge range of supplementary feed options for pregnant ewes in conventional sheep systems, but good-quality organic rations are harder to come by. Michael Gottstein explores the options available.

The majority of foetal growth takes place in the last two months of pregnancy. This is why getting ewe nutrition right at that time is so important in conventional as well as organic systems. On conventional farms the nutritional challenge is easily met by a huge range of supplementary feed options. However, the exclusion of products derived from genetically modified plants and the small organic tillage sector in Ireland means that ingredients to make up good quality organic rations for sheep are hard to come by.

All pregnant ewes have a need for additional energy, protein and minerals/vitamins to meet the requirements of the growing foetus. The conserved roughage/winter forage protein and mineral/vitamins, and the rapid growth of the foetus inhibits the ewe’s ability to consume sufficient roughage.

It is important that heavily pregnant ewes receive sufficient nutrition in late pregnancy to:

• Meet the demands of the unborn lamb(s) ensuring they are well-grown and strong at birth.
• Avoid conditions such as prolapse, milk fever and twin lamb disease.
• Limit the amount of body condition loss in late pregnancy. Ewes that lose a lot of condition in late pregnancy will have a higher likelihood of losing lambs post turnout. Lamb performance will be reduced, regardless of how good post lambing nutrition is.

Energy is the most important component of the late pregnancy diet. Unfortunately, most rations in Ireland are sold based on their protein percentage (eg Ewe 16 or Ewe 18). There is no requirement for manufacturers of sheep feeds to display the amount of energy in the ration. Consequently, the best method for farmers to use when comparing the energy value of different feeds is to look at the ingredients. Table 1, ranks feed ingredients broadly based on their energy values in relative terms. Try to avoid purchasing concentrate feeds that have high levels of ingredients listed in the low energy category. Especially if they are included at significant levels.

There are a number of organic concentrate mixes being imported by Irish millers that contain high levels of Lucerne, oatfeed, wheatfeed and sunflower. These are very low energy rations that are selling in small bags for approx. €900 per tonne. They are extremely bad value and unlikely to deliver the levels of animal performance achieved by cereal-based sheep feeds.

Table 1: Feed ingredients relative energy values

Organic oats and barley

What organic sheep farmers should be looking for in an organic sheep concentrate is wheat, oats, barley and, if available, non-GM maize. Organic oats and barley are widely available at prices from €400 – €450 (oats) €500 - €550 (barley) per tonne with higher protein mixes including peas and beans available for around €680 - €750 per tonne. As always, transport and how the product is delivered (eg bulk versus one tonne bags or 25kg bags) will impact the price. These ingredients on their own with some mineral and vitamin supplementation will deliver high levels of animal performance at more affordable prices.

Protein really only becomes important in the last two to three weeks of pregnancy when the requirement of the ewe almost doubles. From mid pregnancy right up to the last three weeks a 75kg lowland ewe will require around 100 – 130 grams of Crude Protein per day. High quality grass silage or leafy hay will supply most of the protein required by ewes during this time. In the last three weeks of pregnancy, however, the protein requirement rises to 200 – 240 grammes per day. In addition to the amount of protein required, the quality/type of the protein fed at this time is also important.

Bypass protein

There are considerable advantages to supplying a proportion of the protein in a form that avoids digestion in the rumen. This type of protein is often referred to as bypass protein or Digestible Undegradable Protein (DUP). Soyabean meal is the best source of DUP available and should be fed at a rate of 100 grammes per day per lamb carried for the last two weeks of pregnancy.

Mineral and vitamin supplementation is also important, particularly if there is no mineral / vitamin mix included in the concentrate feed. Where straights are being fed then a suitable mineral vitamin mix should be sprinkled on the feed twice daily according to the manufacturer’s recommendations. While minerals are important it is essential not to overfeed them.
Studies have shown that there are negative effects on newborn lambs’ ability to absorb antibodies from colostrum where certain minerals (iodine) have been overfed in late pregnancy.

This is a particular problem where housed sheep are offered unlimited-access mineral lick buckets. Studies have shown that housed ewes consume much higher levels because they lick the buckets out of boredom. This increased intake, as well as being wasteful, can be counterproductive if the increased intake results in excessively high levels of iodine being consumed.

Once you have worked out what type of ration you will feed your ewes the final step is to work out how much supplementation will be required. Table 2 gives guideline figures for twin bearing ewes in good body condition having ad lib access to roughage.

Table 2: Roughage quality guidelines

Silage

Where silage is finely chopped (eg precision chopped) the level of supplementation can be reduced as intakes will be higher. Ewes that are carrying a single lamb should receive 30% less (ie start feeding two weeks later) and ewes carrying triplets should receive 30% more (ie start feeding two weeks earlier).

It is important that once concentrate levels increase above 0.5kg per head per day that they are split into two equal feeds eight hours apart. Also, ensure that ewes have enough trough space. Trough space is a limiting factor on most sheep farms that I visit – 600mm or two feet of head space should be available.

Read more from Today's Farm - January/February 2025